I. Field of the Invention
The present invention relates generally to closure members and, more particularly, to a closure member for a plastic pipe system.
II. Description of the Prior Art
There are a number of previously known closure members which removably close an access opening in a pipe system. Oftentimes the access opening is used as a clean out opening.
Many of these previously known closure members have been externally threaded and cooperate with an internally threaded pipe fitting. Closure members of this type, however, are disadvantageous in that they are both difficult to install and remove and also oftentimes inadequately seal the closure member to the pipe fitting.
One previously known threadless closure member, however, is described in U.S. Pat. No. 3,677,301 which issued on July 18, 1972, and which is commonly owned by the Assignee of the instant application. This previously known threadless closure member is particularly suited for plastic pipe systems and comprises a cylindrical tubular body closed at one end and axially insertable into the pipe access opening. This previously known closure member further included a pair of locking tabs which extended axially along the outer periphery of the pipe fitting following insertion of the closure member into the access opening while a circumferentially extending slot open at one end is formed in each locking tab. The pipe further included a pair of outwardly extending pins so that following insertion of the closure member into the access opening and the subsequent rotation of the closure member, the pins are received within the locking tab slots to lock the closure member against unintended axial displacement of the closure member.
One disadvantage of this previously known closure member, however, is that the closure member can withstand only a predetermined amount of fluid pressure before either the locking tabs and/or the outwardly projecting pins from the pipe break apart due to the force from the fluid pressure. Moreover, many building codes and restrictions for high rise building constructions require that the closure member be able to sustain the water pressure resulting from a head of water of a height equal to the building construction although, in practice, the closure member is never subjected to such high fluid pressures.
Although it would be possible, of course, to increase the size of both the locking tabs and their associated pins in order to increase the fluid pressure capability of the closure member, to do so unduly increases the overall cost of both the pipe fitting and the closure member and is economically infeasible.